Various prior art methods and apparatus have been used to manufacture artificial fuel logs of which I am aware by mixing together sawdust or coal granules with a binder and extruding the mixture into the form of a cylindrical log. In U.S. Pat. No. 2,076,315 to Albrecht, for example, pulverized coal is mixed with Portland cement in a mixing hopper to form a briquette paste that is supplied to a horizontal cylinder for compaction into individual briquettes. The coal and cement, initially combined in the hopper, are temporarily stored in the mixed state prior to compaction into briquettes. In U.S. Pat. No. 4,049,392 to Furman, coal briquettes are formed by an extruder screw that receives a particulate mixture comprising coal and a binder premixed together in a mixing hopper and fed gradually to the extruder as needed during briquette production. In methods of this type, mixing of coal and binder is imperfect, however, causing formation of voids or discontinuities throughout the log. As a result, burning tends to be discontinuous, and there is also a tendency for the outer surface of the log to chip or fracture during shipping, causing the logs to be ultimately unacceptable for commercial sale.
Accordingly, one object of the present invention is to provide a new and improved fuel log that is smooth burning and resistant to chipping or fracturing.
Another object is to provide a method for forming a fuel log from carbonaceous material and binder, wherein particles are bound together to form a continuous mass without voids or discontinuities.
Another object is to provide an apparatus for manufacturing a fuel log, wherein carbonaceous particles are individually and uniformly coated with binder before compaction to eliminate structural voids or discontinuities.
Another object is to provide a method of and apparatus for manufacturing artificial fuel logs that are economical and suitable for mass production.